Change how fence blocks are processed

Use a fixed regex to match all fence blocks, not just the
ones that are modified by this plugin.

de-indent the code block before processing.

This will avoid having wrong matches within a fenced block. ex:

````
Hey, this is just regular text, presenting a plantuml code block.

``` plantuml
@startuml
...
@enduml
```
````

De-indentind the code is necessary if the code block is in a structural
element like a list.
(Apart from being not correct, handling from_file_prefix did not work in
that case)

kroki/config.py

@@ -88,9 +88,5 @@ def __init__(
 
         info(f"File and Diagram types configured: {self.diagram_types_supporting_file}")
 
-    def get_block_regex(self, fence_prefix):
-        diagram_types_re = "|".join(self.diagram_types_supporting_file.keys())
-        return rf"(?P<fence>^([ ]*)(?:````*|~~~~*))[ ]*{fence_prefix}({diagram_types_re})((?:[ ]?[a-zA-Z0-9\-_]+=[a-zA-Z0-9\-_]+)*)\n(.*?)(?<=\n)(?P=fence)[ ]*$"  # noqa
-
     def get_file_ext(self, kroki_type):
         return self.diagram_types_supporting_file[kroki_type]

kroki/plugin.py

@@ -1,6 +1,7 @@
 import hashlib
 import re
 import tempfile
+import textwrap
 
 from functools import partial
 from mkdocs.plugins import BasePlugin
@@ -57,6 +58,13 @@ class KrokiPlugin(BasePlugin):
     from_file_prefix = "@from_file:"
     from_file_prefix_len = len(from_file_prefix)
 
+    _FENCE_RE = re.compile(r"(?P<fence>^(?P<indent>[ ]*)(?:````*|~~~~*))[ ]*"
+                           r"(\.?(?P<lang>[\w#.+-]*)[ ]*)?"
+                           r"(?P<opts>(?:[ ]?[a-zA-Z0-9\-_]+=[a-zA-Z0-9\-_]+)*)\n"
+                           r"(?P<code>.*?)(?<=\n)"
+                           r"(?P=fence)[ ]*$",
+                           flags=re.IGNORECASE + re.DOTALL + re.MULTILINE)
+
     def on_config(self, config, **_kwargs):
         info(f"Configuring: {self.config}")
 
@@ -119,12 +127,7 @@ def _save_kroki_image_and_get_url(self, file_name, image_data, files):
 
         return f"{self._site_url}{mkdocs_file.url}"
 
-    def _replace_kroki_block(self, match_obj, files, page):
-        kroki_indent = match_obj.group(2)
-        kroki_type = match_obj.group(3).lower()
-        kroki_options = match_obj.group(4)
-        kroki_data = match_obj.group(5)
-
+    def _replace_kroki_block(self, kroki_type, kroki_options, kroki_data, files, page):
         if kroki_data.startswith(self.from_file_prefix):
             file_name = kroki_data[self.from_file_prefix_len :].strip()  # noqa
             file_path = self._docs_dir / file_name
@@ -159,20 +162,29 @@ def _replace_kroki_block(self, match_obj, files, page):
             )
 
         if get_url is not None:
-            return kroki_indent + f"![Kroki]({get_url})"
+            return f"![Kroki]({get_url})"
 
         return f'!!! error "Could not render!"\n\n```\n{kroki_data}\n```'
 
     def on_page_markdown(self, markdown, files, page, **_kwargs):
         debug(f"on_page_markdown [page: {page}]")
-
-        kroki_regex = self.diagram_types.get_block_regex(self.fence_prefix)
-        pattern = re.compile(kroki_regex, flags=re.IGNORECASE + re.DOTALL + re.MULTILINE)
+        key_types = self.diagram_types.diagram_types_supporting_file.keys()
+        fence_prefix = self.fence_prefix
 
         def replace_kroki_block(match_obj):
-            return self._replace_kroki_block(match_obj, files, page)
+            kroki_type = match_obj.group('lang').lower()
+            if kroki_type.startswith(fence_prefix):
+                kroki_type = kroki_type[len(fence_prefix):]
+
+            if kroki_type not in key_types:
+                # Not supported, skip over whole block
+                return match_obj.group()
+
+            return match_obj.group('indent') + \
+                self._replace_kroki_block(kroki_type, match_obj.group('opts'), textwrap.dedent(match_obj.group('code')),
+                                          files, page)
 
-        return re.sub(pattern, replace_kroki_block, markdown)
+        return re.sub(self._FENCE_RE, replace_kroki_block, markdown)
 
     def on_post_build(self, **_kwargs):
         if hasattr(self, "_tmp_dir"):